Various types of resin films are used in liquid crystal display devices. Among these, triacetyl cellulose is commonly used in polarizer protective films. However, a high moisture permeability of a film comprising triacetyl cellulose tends to deteriorate polarizers as the film thickness becomes thinner. Improvement of polarizer protective films has been an issue for thinner liquid crystal displays.
Accordingly, methacrylic resins have been researched as new materials for polarizer protective films. It is known that stretch treatment of a film comprising a methacrylic resin increases toughness of the film (see Patent Document 1). However, a stretched film comprising a methacrylic resin is susceptible to thermal shrinkage because the glass transition temperature of a common methacrylic resin is as low as about 110° C.
Methacrylic resins are known to have higher glass transition temperatures as the syndiotacticity increases. Examples of a method of manufacturing a methacrylic resin having a high syndiotacticity can include those involving anionic polymerization (Patent Documents 2 and 3). However, due to poor formability of a methacrylic resin obtainable by these methods, a film comprising the above methacrylic resin tends to have poor surface smoothness. Although it is known that decreasing molecular weight can improve forming processability, another problem may arise that the mechanical strength of the resulting film is decreased. For this reason, a film comprising a methacrylic resin having a high syndiotacticity has not yet been available for practical use.